New Nanomaterial NanoBuds Combines Fullerenes and Nanotubes

first_img Citation: New Nanomaterial, ‘NanoBuds,’ Combines Fullerenes and Nanotubes (2007, March 30) retrieved 18 August 2019 from https://phys.org/news/2007-03-nanomaterial-nanobuds-combines-fullerenes-nanotubes.html Researchers have created a hybrid carbon nanomaterial that merges single-walled carbon nanotubes and spherical carbon-atom cages called fullerenes. The new structures, dubbed NanoBuds because they resemble buds sprouting on branches, may possess properties that are superior to fullerenes and nanotubes alone. They are described in the March 2007 edition of Nature Nanotechnology. Explore further The search for new materials for hydrogen storage “Both fullerenes and single-walled carbon nanotubes exhibit many advantageous properties, but despite their similarities there have been very few attempts to physically merge them. The novel hybrid material we discovered merges the two into a single structure, in which the fullerenes are covalently bonded to the nanotubes,” said Esko Kauppinen, a scientist involved in the work, to PhysOrg.com. Kauppinen is a professor and researcher at the Helsinki University of Technology and the technology development organization VTT Biotechnology, both in Finland.Synthesis of the NanoBuds began with the synthesis of single-walled carbon nanotubes (SWNTs) in a standard reactor. The resulting SWNTs seemed to be coated with clusters of carbon atoms, but a closer investigation, using an electron microscope, revealed that most of the clusters were actually fullerenes.The fullerenes coating the nanotubes displayed unusual behavior. Using a transmission electron microscope, the researchers saw that these fullerenes did not move around upon the nanotube surface. This in not typical of fullerenes on SWNTs and indicated a strong fullerene/nanotube bond, which was further verified by several tests.The group further probed the NanoBuds’ structure using ultraviolet spectroscopy. The resulting UV spectra showed the attached fullerenes to be similar to C70, the 70-carbon-atom fullerene, which has a slightly ellipsoidal shape compared to C60 and other spherical fullerenes. This deviation from the characteristic fullerene sphere, or “bucky ball,” could have been due to the presence of covalently attached oxygen or hydrogen. Further measurements detected oxygen in each NanoBud, and a round of infrared spectroscopy revealed the presence of two types organic compounds known as ethers and esters. These compounds may act as bridge-like structures connecting the fullerenes to the nanotubes.Kauppinen and his colleagues say that NanoBuds may find use as cold electron field emitters – materials that emit electrons at room temperature under a high applied electric field – due to the fullerenes’ many curved surfaces, which make for better emitters that flat surfaces. Cold electron field emission is key to many technologies, including flat-panel displays and electron microscopes.“We believe that NanoBuds may have other applications, such as molecular anchors to prevent SWNTs from slipping within composite materials,” says Kauppinen. “Additionally, since the optical and electrical properties of the fullerenes and nanotubes can be individually tuned, NanoBuds provide SWNTs with distinct regions of different electrical properties. This could be useful for many applications, including memory devices and quantum dots.”Citation: Albert G. Nasibulin, Peter V. Pikhitsa, Hua Jiang, David P. Brown, Arkady V. Krasheninnikov, Anton S. Anisimov, Paula Queipo, Anna Moisala, David Gonzalez, Günther Lientschnig, Abdou Hassanien, Sergey D. Shandakov, Giulio Lolli, Daniel E. Resasco, Mansoo Choi, David Tománek and Esko I. Kauppinen, “A novel hybrid carbon material.” Nature Nanotechnology 2, 156-161 (2007)Copyright 2007 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. (left) Two transmission electron microscope images of a single-walled carbon nanotube with fullerenes attached to its surface (right) A fullerene/SWNT hybrid structure – a NanoBud. Credit: Esko Kauppinen, et al. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Researchers uncover secrets of miracle fruit

first_img Food peptides activate bitter taste receptors (PhysOrg.com) — Though not very well known in the United States, at least until the past few years, the miracle fruit is a cranberry like fruit that has the unique property of being able to make acidic or bitter foods taste sweet. And while the protein that makes this possible has been known for quite a while, just how exactly it did its trick has been a mystery; until now. A team of Japanese and French researchers working together have solved the puzzle and have published the results of their efforts in the Proceedings of the National Academy of Sciences. Miracle fruit, the berry of the Synsepalum dulcificum plant, grows naturally in West Africa and the locals there have long known of its sweetening properties. Pop one of the little berries in the mouth and for an hour, foods like pickles, beer, grapefruit or lime, taste like sweet versions of their former selves. More recently, the effects of the miracle fruit have been popularized by flavor-tripping parties, so named because of the odd sensational resemblance to the effects of hallucinogens. Or as Keiko Abe, one of the team leads, reports, the effect is rather magical.To get to the bottom of how the miracle fruit performs its magic, the team grew human kidney cells in a dish that were engineered to produce sweet receptor proteins. They then applied a chemical that caused the receptor cells to light up when activated. Next, they applied miraculin, the protein in miracle fruit that is responsible for the sweetening effects. After that they added different substances with different pH levels and found that the miraculin had three distinct impacts on the receptors. At low levels there is little effect, at medium levels the miraculin boosted response and at high levels the receptors were activated on their own.This all happens, the researchers say, because the miraculin protein changes shape when exposed to acids. The higher the level, the more it changes shape. And because the protein binds very strongly to the receptors in the human tongue, those changes in shape change the way the receptors react when acids are introduced into the mouth. The bottom line is, the higher the pH level in a substance, the sweeter it tastes to the person doing the tasting.The end result of this research might be the introduction of a whole new kind of artificial sweetener, either as an ingredient, or as an additive by users wishing only to sweeten ordinary foods. And now that the effects of miraculin are better understood, researchers will next try to see if they can create it from scratch rather than having to rely on Mother Nature to grow it for them. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Photo of Miracle berry (Hamale Lyman/Wikipedia) Citation: Researchers uncover secrets of ‘miracle fruit’ (2011, September 27) retrieved 18 August 2019 from https://phys.org/news/2011-09-uncover-secrets-miracle-fruit.html Explore further More information: Human sweet taste receptor mediates acid-induced sweetness of miraculin, PNAS, Published online before print September 26, 2011, doi: 10.1073/pnas.1016644108AbstractMiraculin (MCL) is a homodimeric protein isolated from the red berries of Richadella dulcifica. MCL, although flat in taste at neutral pH, has taste-modifying activity to convert sour stimuli to sweetness. Once MCL is held on the tongue, strong sweetness is sensed over 1 h each time we taste a sour solution. Nevertheless, no molecular mechanism underlying the taste-modifying activity has been clarified. In this study, we succeeded in quantitatively evaluating the acid-induced sweetness of MCL using a cell-based assay system and found that MCL activated hT1R2-hT1R3 pH-dependently as the pH decreased from 6.5 to 4.8, and that the receptor activation occurred every time an acid solution was applied. Although MCL per se is sensory-inactive at pH 6.7 or higher, it suppressed the response of hT1R2-hT1R3 to other sweeteners at neutral pH and enhanced the response at weakly acidic pH. Using human/mouse chimeric receptors and molecular modeling, we revealed that the amino-terminal domain of hT1R2 is required for the response to MCL. Our data suggest that MCL binds hT1R2-hT1R3 as an antagonist at neutral pH and functionally changes into an agonist at acidic pH, and we conclude this may cause its taste-modifying activity. © 2011 PhysOrg.comlast_img read more

HighTech fishing net finalist for Dyson Award

first_img Citation: High-Tech fishing net finalist for Dyson Award (2012, August 31) retrieved 18 August 2019 from https://phys.org/news/2012-08-high-tech-fishing-net-finalist-dyson.html Explore further More information: www.jamesdysonaward.org/Projec … gionId=19&Winindex=0 The rings are big enough for small fish to swim through, but not so big that larger fish can do the same. They are sewn into the net, in effect, creating holes, just at the part of the net where the fish are pushed due to current flow. The rings also light up, helping the little fish see where the outlets are, serving as guide signs. And that’s not all, one variant of the rings uses kinetic energy derived from water rushing through the rings to power the lights, the other uses batteries.The James Dyson Award was established by the James Dyson Foundation to reward innovative designs and to inspire new ways of thinking by college students or those, such as Watson, who have recently graduated. The winner, in addition to worldwide accolades also receives £10,000 for him or herself, another £10,000 for their school and a certificate.Because the rings are made of hard plastic, they prevent the collapse or tears that would occur were the nets to simply have small holes cut in them. Watson has already sea tested the nets, of course, and the results were good enough to push him to the finals. He believes that if commercial fishermen would add the rings to their nets, on average about 20 would be needed for each net, fish populations would rise and fishermen would save time on not having to cull. He expects the rings would cost about £25 apiece once produced in mass quantities. Researcher shows fishing has reduced salmon size in Alaska (Phys.org)—Dan Watson, a Glasgow School of Art graduate, has won the UK leg of the James Dyson award for his innovative fishing net rings that light up and guide smaller fish through nets meant for larger prey. Called SafetyNet, the rings prevent smaller fish being thrown back dead into the sea after being culled. He along with seventeen other finalists will vie for the prestigious grand prize which will be announced November 8. Trawler fishing is where boats move slowly over the surface of the water with nets hanging down to capture fish swimming below. Unfortunately, the nets catch everything in their path, including those that are too small to sell. Fishermen are forced to sort out the big from the small resulting in a lot of time spent and dead fish being tossed back into the sea. Watson, with his SafetyNet, hopes to change that. © 2012 Phys.org This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Statisticians try to calculate probability of another 911 sized attack

first_img Journal information: arXiv (upper) Number of deadly (domestic and international) terrorist events worldwide for the ten year period 1998–2007, and three forecast scenarios. (lower) Fraction of events that are severe, killing at least 10 individuals and its 10-year average (dashed line). Credit: arXiv:1209.0089v1 [physics.data-an] (Phys.org)—In the world of probability and statistics almost anything can be labeled as a percentage of likelihood of occurring; statistics based on actual numbers give rise to probabilistic estimates that in some cases may be very accurate, not so accurate, or impossible to prove one way or another. With such a view, two statisticians, Aaron Clauset and Ryan Woodard have trained their sights on terrorist incidents and the likelihood of them occurring, specifically, the big kinds, like 9/11. They have found, as they describe in their paper they’ve uploaded to the preprint server arXiv, that using tried and true statistical models, that the likelihood of another attack as big, or even bigger, than 9/11, is as likely as not. The basis of any statistical model is data and in this case the data was based on the number of terrorist acts committed between the years 1969 and 2007, which of course included 9/11. The attack on the twin towers in New York stands out of course, as the number of people killed that day was six times more than any other terrorist attack. To first see how accurate any given model might be, the researchers calculated the likelihood of 9/11 actually happening based on prior data using three different types of standard models; power law, exponential distributions and log-normal. After crunching the numbers they say it came down to between an eleven to thirty five percent chance, which they say is reasonable and shows that what happened on 9/11 was not unlikely, statistically speaking, to have happened.The two then applied the same models looking forward into the future and came up with a likelihood of another 9/11 type attack falling between twenty and fifty percent, depending on which model was used and assuming that things remain the same, i.e. the average number of attacks per year (approximately 2000) stays the same. But, realizing that the odds of things holding steady isn’t itself very realistic they also tried factoring in such destabilizing scenarios as rising food prices or things calming or growing worse in two of the current hot spots for terrorism; Iraq and Afghanistan. In such cases the models became truly alarming, indicating that in the worst case scenarios the likelihood of another event as deadly as 9/11 occurring, becomes nearly ninety five percent. Terrorism and the Olympics by-the-numbers: Analysis from UMD-based START Explore furthercenter_img More information: Estimating the historical and future probabilities of large terrorist events, arXiv:1209.0089v1 [physics.data-an] arxiv.org/abs/1209.0089AbstractQuantities with right-skewed distributions are ubiquitous in complex social systems, including political conflict, economics and social networks, and these systems sometimes produce extremely large events. For instance, the 9/11 terrorist events produced nearly 3000 fatalities, nearly six times more than the next largest event. But, was this enormous loss of life statistically unlikely given modern terrorism’s historical record? Accurately estimating the probability of such an event is complicated by the large fluctuations in the empirical distribution’s upper tail. We present a generic statistical algorithm for making such estimates, which combines semi-parametric models of tail behavior and a non-parametric bootstrap. Applied to a global database of terrorist events, we estimate the worldwide historical probability of observing at least one 9/11-sized or larger event since 1968 to be 11-35%. These results are robust to conditioning on global variations in economic development, domestic versus international events, the type of weapon used and a truncated history that stops at 1998. We then use this procedure to make a data-driven statistical forecast of at least one similar event over the next decade. © 2012 Phys.org Citation: Statisticians try to calculate probability of another 9/11 sized attack (2012, September 10) retrieved 18 August 2019 from https://phys.org/news/2012-09-statisticians-probability-sized.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

New research suggests tropical cyclones could develop on Saturns largest moon Titan

first_img(Phys.org) —Planetary scientist Tetsuya Tokano of Germany’s University of Cologne has found that the right ingredients might exist on Titan, Saturn’s largest moon, for the formation of tropical cyclones. In his paper published in the journal Icarus, Tokano says that if one the seas on Titan contains enough methane, then all the conditions could be present for the formation of the mini-hurricanes. What caused a giant arrow-shaped cloud on Saturn’s moon Titan? Titan is Saturn’s largest moon and is the only known natural satellite with a dense atmosphere. Its mass is roughly 80 percent larger than that of Earth’s moon, and because of the great distance from the sun, experiences year-round very low temperatures. And while its body is made mostly of a mix of rocks and frozen water, it has an atmosphere that is mostly nitrogen with some ethane and methane. Titan is also the only known moon in the solar system (besides Earth) to have liquid on its surface, and because of that, rainfall. Tokano believes Titan is capable of spawning tropical cyclones because he thinks one or more of the seas on the moon is not only large enough, but has enough methane in it to give rise to the storms—researchers can’t say for sure whether this is the case or not because past observations of the moon have been obscured by the dense atmosphere, making it difficult to determine what lies below.Tropical cyclones are spinning storms that develop on Earth when warm ocean water evaporates into the air, carrying with it enough energy to spawn spinning storms. On Earth, such storms generally develop around the equator, in the tropics, hence their name. On Titan, things would be a lot different as all of the seas that could be capable of generating such storms are located near its North Pole.In studying the topology of Titan, Tokano noted that the moon has at least three seas that should be large enough to support the formation of tropical cyclones, provided there is enough methane in them. He suggests that when methane evaporates up out of a sea during its summer season, it would carry with it heat that would be converted into kinetic energy—enough to drive the formation of a swirling storm. He notes that over the next few years, Titan will be entering its summer season, providing researchers monitoring data from Cassini—the spacecraft orbiting Saturn—an opportunity to see if the distant moon is indeed experiencing any tropical cyclones. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Explore further More information: Tetsuya Tokano, Are tropical cyclones possible over Titan’s polar seas? Icarus, Available online 8 February 2013 dx.doi.org/10.1016/j.icarus.2013.01.023 AbstractWhile extratropical cyclones cannot be expected in Titan’s barotropic troposphere, tropical cyclones which gain their energy from the latent heat of sea evaporation cannot be entirely dismissed over Titan’s polar hydrocarbon seas. The most essential condition for the genesis of tropical cyclones on Titan is a methane-rich composition of the polar seas. The most likely season for Titan’s hypothetical tropical cyclones is around the northern summer solstice when the sea surface gets warmer and the relative vorticity of the near-surface air increases by seasonal convergence and equatorial wave activity. A tropical cyclone would manifest itself as an anti-clockwise swirling vortex right over one of the northern seas (Kraken Mare, Ligeia Mare, Punga Mare) and increase the surface wind over the seas by an order of magnitude. On the other hand, tropical cyclones are unlikely to emerge over Titan’s few tropical lakes for dynamic reasons such as negligible Coriolis parameter and large vertical wind shear.center_img Journal information: Icarus Titan’s hazy orange globe hangs before the Cassini spacecraft. Image credit NASA/JPL/Space Science Institute. Citation: New research suggests tropical cyclones could develop on Saturn’s largest moon Titan (2013, March 21) retrieved 18 August 2019 from https://phys.org/news/2013-03-tropical-cyclones-saturn-largest-moon.html © 2013 Phys.orglast_img read more

The Velkess Flywheel A more flexible energy storage technology

first_img More information: www.kickstarter.com/projects/1 … kess-energy-storage#velkess.com/www.google.com/patents/EP2232680A1 (Phys.org) —A new Kickstarter project called Velkess (Very Large Kinetic Energy Storage System) has recently gotten underway to bring an inexpensive flywheel to market. The project is headed by Bill Gray, who has taken a unique approach to flywheel design—a flexible rotor made of “E-glass,” a common fiberglass used in everything from sporting goods to shower doors. Rather than use advanced carbon-fiber composites manufactured to exact tolerances, Gray’s soft rotor flexes in response to destabilizing forces. It is thereby able to adjust to speed transitions that confound other designs. With the memory of other flywheel venture failures, like Beacon, fresh in mind, Gray has cast the issues a little differently. While carbon fiber reinforced polymer is 6 to 8 times stronger than E-glass, he notes that E-glass is 10 to 20 times stronger per dollar. Similarly, E-glass will store 10 to 20 times more energy per dollar. The current prototype floats on a magnetic bearing assembly that can handle 2kW of power, and store 0.5 kWh of energy. Their final device will need storage closer to 15kWh to meet the first projected 48-volt off-grid power backup.This scale up means replacing the 25lb flywheel rotor used for the video footage with a 750lb rotor. Scale-up creates new issues including special production runs for magnets able to support that load, and also equipment to safely handle all that magnetic force floating around. Details of the bearing-motor assembly are still not publicly available. Since the rotor design is essentially cantilevered from the motor in the vertical plane, anything here is possible. For example it appears that the rotor has a low-end speed of 9000 RPM. That would be where it is not even transitioning power. To get to the 15kWh regime, we are probably talking about a max RPM on the order of that of a jet engine. Jet engine speeds are well above even the fastest comparable electric motor speeds. For example, high-speed spindles for machine tools, that might put out anything approaching say 30kW, would probably max out below 10,000 RPM—and these motors can cost over $50,000. Probably some fancy gearing is involved here, and therefore ample opportunity for unique combinations of bearings to be employed throughout the system. Where mechanical bearings are to be used, they can have thermal sensors to detect any rise in temperature that would indicate a failure may be about to occur. The possibility for catastrophe due to fracture in one of the silicon nitride bearings can be therefore be greatly reduced. In an off-grid shutdown, the device would dissipate its energy in the form of exhausted hot air. As the rotor slowed over the course of ten hours, this would be a similar flow as a 1500-watt hair dryer might put out.Gray expects the final units to be comparable in price to lead acid batteries while having a much improved lifetime. Also, the construction materials will be environmentally friendly. The rotor will operate in a vacuum and it is expected that only about 2 percent of its stored power will be lost to friction each day. These numbers make the new flywheel design look like it could be a viable alternative not just to batteries but also to other green schemes like compressed air storage, or pumping water uphill. If the Velkess project can get backing on a scale similar to what these technologies have attracted, flywheels may have finally come of age. Velkess Flywheel © 2013 Phys.org This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Tilting at wind farms Citation: The Velkess Flywheel: A more flexible energy storage technology (2013, April 12) retrieved 18 August 2019 from https://phys.org/news/2013-04-velkess-flywheel-flexible-energy-storage.html Explore furtherlast_img read more

Nanoscale neighbors First use of transformation optics to accurately analyze nonlocality in

first_imgThe schematic of the problem. A dimer of separated nanospheres where the surface charge smearing is described by an effective cover layer of (A) a constant thickness Δd’, (B) a constant permittivity, εS =1 (shifting the metal boundary by Δd’), or (C) a variable thickness Δd’ and spatially dependent permittivity. Under an inverse transformation, the asymmetric core-shell structure in C can be mapped to a dielectric annulus (shown in D) defined by a dielectric-coated metal sphere and a dielectric-coated hollow sphere. Credit: Luo Y, Zhao R, Pendry JB (2014) van der Waals interactions at the nanoscale: The effects of nonlocality. Proc Natl Acad Sci USA 111(52):18422-18427. · the fact that the forces depend on contributions from many different frequencies over a range of almost 100eVPendry notes that researchers are only now beginning to explore the consequences of nonlocality in nanoscale surface phenomena, and are in the process of building reliable models. “The nanoscale forces in our paper are just one instance of where it’s important to treat nonlocality, where the main complication is that the response of a system at a given point depends not just on the electromagnetic fields at that point, but on the fields in the surrounding region as well – a problem that many traditional approaches fail to address.”In their paper, the scientists found that nonlocality dramatically weakens the field enhancement between the spheres, and thereby the van der Waals interaction. “van der Waals forces – although long range relative to standard chemical bonds – are only significant when surfaces are quite close to one another,” Pendry explains. “The standard local theory predicts infinite force in the limit that surfaces touch – but of course this is nonsense. Therefore, predictions that make sense and can be compared to experiments need to take nonlocality into account.”Relatedly, the paper states that chemical bonding – while not an explicit concern in this study – will dominate the final approach just before the surfaces touch at a few tenths of a nanometer, at which point direct contact of the charges will come into play through electron tunneling. “The forces we consider are complementary to chemical bonding,” Pendry clarifies, “in that the current theoretical approach to chemical bonds exploits the local density approximation. In other words, just as a study of pure van der Waals forces omits chemical bonding, so a pure local density study of bonds has nothing to say about the longer range dispersion forces that we calculate. Of course, at some stage the two have to come together…but for that to happen we need experimental input – and theoretical studies of the van der Waals forces are the first steps in making this happen.”The approach described in the paper makes analytical investigation of 3D nonlocal problems feasible while providing insight into the understanding of nonlocal effects in plasmonic nanostructures. “Calculations are always difficult when treating singular structures – by which we mean situations such as the nearly touching spheres considered in our paper – but also the interaction of needle-sharp points with surfaces,” Pendry explains. “Using transformations to unravel the singularity reveals how the forces work in each of these situations, and in fact often enables us to show a common origin.” For example, regarding how their results might influence the development of functional subnanometer substrates, he adds that “any nanomechanical system must consider the effects of van der Waals forces – and our paper is an attempt to further our understanding of these problems.”Looking ahead, Pendry tells Phys.org that van der Waals forces are just the first step in a series of investigations the scientists have already planned. “On the near horizon is heat transfer between surfaces that are close but not in physical contact: Electromagnetic fluctuations responsible for the van der Waals force also enable heat to leap across the gap – an effect different from, and much stronger than, radiative cooling.” (Radiative cooling is the process by which a body loses heat by thermal radiation.) “In the longer term, we’ll try to generalize our theory of quantum friction, whereby surfaces which are close but not in physical contact can experience frictional drag. Nonlocality is also an important issue in the effects.”In closing, Pendry notes that several other areas of research might benefit from their study, given that transformation optics is a very general technique in electromagnetic theory. “The present study is just one in a whole series of applications. We’ve already seen many studies of its application to invisibility, and we have used it extensively to study intense field enhancements in plasmonic structures, such as surface enhanced Raman spectroscopy. In fact, virtually any problem that has electromagnetic radiation interacting with a physical structure could potentially benefit from transformation optics – and in the case of plasmonic systems, nonlocality will always be an important issue whenever surface in close proximity are considered.” Citation: Nanoscale neighbors: First use of transformation optics to accurately analyze nonlocality in 3D plasmonic systems (2015, January 2) retrieved 18 August 2019 from https://phys.org/news/2015-01-nanoscale-neighbors-optics-accurately-nonlocality.html Explore further · the problem involved several length scales, meaning that they had to take into account the spheres themselves (~10nm) as well as the spacing between them, which they tried to push to the limit of one atomic spacing (~0.2nm) (Phys.org) —The ubiquitous van der Waals interaction – a consequence of quantum charge fluctuations – includes intermolecular forces such as attraction and repulsion between atoms, molecules and surfaces. The most long-range force acting between particles, it influences a range of phenomena including surface adhesion, friction and colloid stability. Typically a simple task when parallel surfaces are further apart than 10 nanometers, calculating van der Waals forces between, for example, a pair of nanospheres less than five nanometers apart becomes quite difficult. Moreover, the latter scale requires that the effect of nonlocality (the direct interaction of two objects that are separated in space with no perceivable intermediate agency or mechanism) be considered, introducing complexity into, and thereby further hampering, analysis. More information: van der Waals interactions at the nanoscale: The effects of nonlocality, Proceedings of the National Academy of Sciences, published online before print December 2, 2014, doi:10.1073/pnas.1420551111 Van der Waals force re-measured: Physicists verify nonlinear increase with growing molecular size The absorption spectrum for a dimer of spherical particles. The contour plot of the absorption cross section vs. the frequency and the separation for a pair of gold nanospheres with equal radii of (A) 5 and (B) 30 nm. Comparison of our analytical calculations with local and nonlocal numerical simulations for two closely separated (δ =0:2 nm) gold spheres with equal radii of (C) 5 and (D) 30 nm. Credit: Luo Y, Zhao R, Pendry JB (2014) van der Waals interactions at the nanoscale: The effects of nonlocality. Proc Natl Acad Sci USA 111(52):18422-18427. Journal information: Proceedings of the National Academy of Sciences © 2015 Phys.org Recently, however, scientists at Imperial College London, London proposed a simple analytic solution, showing – for the first time, the researchers say –that nonlocality in 3D plasmonic systems can be accurately analyzed using transformation optics. (Plasmons are quasiparticles arising from the quantization of plasma oscillations at optical frequencies; by arranging electromagnetic fields in a specific way, transformation optics determines the direction in which electromagnetic radiation will propagate.) The scientists also suggest that their results increase the underlying understanding of nonlocal effects in plasmonic nanostructures.Prof. Sir John Pendry discussed the paper that he, Dr. Yu Luo and Dr. Rongkuo Zhao published in the Proceedings of the National Academy of Sciences. “Nonlocality introduces computational complexity which makes doing the calculations difficult,” Pendry tells Phys.org. “We’ve found a workaround that greatly simplifies the calculations by replacing the nonlocal system with a local system that reproduces the results to a high degree of accuracy.” Specifically, the scientists showed that nonlocality in 3D plasmonic systems can be accurately analyzed using the transformation optics approach – the first time that the technique has been applied to van der Waals forces – which they applied to solve the problem of including nonlocal effects when two nanoscale bodies interact. “The key to successfully exploiting transformation optics,” Pendry points out, “is to choose the right transformation. In our case we were able to transform the problem of two nearly-touching spheres into the much more symmetric problem of two concentric spheres.” In so doing, the researchers had to address two challenges: This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Zooplankton filmed eating bits of plastic trash

first_img(Phys.org)—A team of researchers and Verity White (a noted producer and director of nature films) has captured, for the first time on film, zooplankton feeding on bits of plastic—the type that has made its way into the world’s oceans due to human dumping. The team has published its findings in the journal Environmental Science and Technology and has also released the videos they made of the zooplankton in action. In recent years it has come to the public’s attention that massive amounts of trash are being dumped into the world’s oceans and a lot of that trash is in the form of various types of plastics—some estimate as much as eight million tons of the stuff every year goes into the ocean, helping form in some cases, huge trash islands. Plastics can take ten to twenty years to degrade and besides being unsightly, they can cause problems when marine animals eat them. Even after plastic material starts to break down it can cause problems because as it does so, it degrades into tiny particles (microplastics) which it now appears are consumed by zooplankton—a generic name given to a wide variety of mostly microscopic sized organisms that live near the surface in the sea—from crab and lobster larvae to tiny worms and pteropods. To determine if tiny zooplankton ingest plastic particles as they go about attempting to eat their normal diet of algae, the researchers placed copepod specimens in a tank at their lab in Plymouth Marine Laboratory and filmed them as they fed. Such creatures use their legs to create a current which draws algae to them—to differentiate between plastic and other material in the water, the researchers used fluorescent beads which could be seen in both the water and in the bodies of the copepod after they ate them. The researchers noted that the plastic beads remained in the body of the animals anywhere from a few hours to a week, which suggests that in the natural environment, animals that live off zooplankton are ingesting the plastic when they feed, resulting in plastics bits making their way all the way up the food chain. In other experiments, the team reports that other types of zooplankton were also observed ingesting microplastics and that the creatures that ate the plastic tended to ingest less algae, which suggests they would provide less energy to other creatures that feed on them. Journal information: Environmental Science and Technology Citation: Zooplankton filmed eating bits of plastic trash (2015, July 10) retrieved 18 August 2019 from https://phys.org/news/2015-07-zooplankton-bits-plastic-trash.html © 2015 Phys.org Explore further More information: Microplastic Ingestion by Zooplankton, Environ. Sci. Technol., 2013, 47 (12), pp 6646–6655. DOI: 10.1021/es400663fAbstractSmall plastic detritus, termed “microplastics”, are a widespread and ubiquitous contaminant of marine ecosystems across the globe. Ingestion of microplastics by marine biota, including mussels, worms, fish, and seabirds, has been widely reported, but despite their vital ecological role in marine food-webs, the impact of microplastics on zooplankton remains under-researched. Here, we show that microplastics are ingested by, and may impact upon, zooplankton. We used bioimaging techniques to document ingestion, egestion, and adherence of microplastics in a range of zooplankton common to the northeast Atlantic, and employed feeding rate studies to determine the impact of plastic detritus on algal ingestion rates in copepods. Using fluorescence and coherent anti-Stokes Raman scattering (CARS) microscopy we identified that thirteen zooplankton taxa had the capacity to ingest 1.7–30.6 μm polystyrene beads, with uptake varying by taxa, life-stage and bead-size. Post-ingestion, copepods egested faecal pellets laden with microplastics. We further observed microplastics adhered to the external carapace and appendages of exposed zooplankton. Exposure of the copepod Centropages typicus to natural assemblages of algae with and without microplastics showed that 7.3 μm microplastics (>4000 mL–1) significantly decreased algal feeding. Our findings imply that marine microplastic debris can negatively impact upon zooplankton function and health. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Microplastics endanger ocean healthlast_img read more

Researchers find proof that oysters turn pearls as part of development process

first_img © 2015 Phys.org Citation: Researchers find proof that oysters turn pearls as part of development process (2015, July 15) retrieved 18 August 2019 from https://phys.org/news/2015-07-proof-oysters-pearls.html Credit: NOAA Journal information: Royal Society Open Science This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. For many years researchers and others have speculated on the process that goes on inside of an oyster that results in the formation of a pearl (the only gem produced by an organism), especially the ones that are very nearly perfectly round. Many have suggested that in order for such pearls to come about, it must have been rotated inside the oyster—also markings on many pearls have suggested spinning. But until now, no one has been able to definitively prove that the pearl was turned.Pearls are created in many mollusks, not just oysters, and their development is due to a reaction by the mollusk to an invading bit of material. Because the insides of mollusks are delicate, they need to protect themselves against material that can cause harm—when a bit of sand or silica is detected in the mantel tissue, the mollusk creates a cover for it (called the pearl sac) and adds a material it secretes called nacre (made up mostly of calcium carbonate)—then, according to the researchers, they spin the material to smooth out rough edges.The researchers were able to make this discovery by using a specially modified magnetometer to watch the pearl inside of an oyster as it developed—it allowed for registering magnetic field variations inside the oyster due to magnetic material that was inserted into the pearl center. The setup allowed the researchers to “see” the developing pearl being turned starting after 40 days had passed and continuing on until the pearl was harvested after approximately a year. They report that the pearl was turned at a rate of 1.27° min−1 (averaged over four pearls) and that pearl shape and defects appeared to be impacted when rotating was interrupted.The team also used high magnification techniques to examine patterns that appeared on the surface of pearls during the development process and found that when bumps and grooves appear, the result is irregular notches, whereas those pearls that were more rounded tended to have more precise spiral shapes.center_img (Phys.org)—A team of researchers with members affiliated with institutions in French Polynesia, France and Qatar has finally proved that pearls do spin inside of oysters as they develop. In their paper published in Royal Society Open Science, the team describes their technique and other aspects of peal development they were able to observe. Explore further More information: Yes, it turns: experimental evidence of pearl rotation during its formation, Royal Society Open Science, DOI: 10.1098/rsos.150144AbstractCultured pearls are human creations formed by inserting a nucleus and a small piece of mantle tissue into a living shelled mollusc, usually a pearl oyster. Although many pearl observations intuitively suggest a possible rotation of the nucleated pearl inside the oyster, no experimental demonstration of such a movement has ever been done. This can be explained by the difficulty of observation of such a phenomenon in the tissues of a living animal. To investigate this question of pearl rotation, a magnetometer system was specifically engineered to register magnetic field variations with magnetic sensors from movements of a magnetic nucleus inserted in the pearl oyster. We demonstrated that a continuous movement of the nucleus inside the oyster starts after a minimum of 40 days post-grafting and continues until the pearl harvest. We measured a mean angular speed of 1.27° min−1 calculated for four different oysters. Rotation variability was observed among oysters and may be correlated to pearl shape and defects. Nature’s ability to generate so amazingly complex structures like a pearl has delivered one of its secrets. Pearly perfectionlast_img read more

Best of Last Week—Roundest object ever found taking aim at fake news

first_img This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. (Science X)—It was a big week for space science as a team with members from the Max Planck Institute for Solar System Research and the University of Göttingen found that a distant star was the roundest object ever observed in nature—they found that the difference between the equatorial and polar radii of a star named Kepler 11145123 was only 3 kilometers. A team with NASA’s THEMIS mission reported that they had found unusual origins of high-energy electrons that gain energy through electromagnetic activity in the foreshock region. And a team working on the New Horizons mission found evidence that suggested a water-ice ocean lies beneath Pluto’s heart-shaped basin. Also, a Dutch firm unveiled a concept space suit for Mars explorers—Mars One showed off the suits, which are similar to those used by astronauts that went to the moon, but have extra features to deal with the red dust. And a team with Swinburne University of Technology and the University of Cambridge announced that they’d found evidence of a cosmic ‘barcode’ from a distant galaxy that confirms nature’s constancy—showing that electromagnetism in a distant galaxy has the same strength as it does here on Earth.In other news, a team of researchers at the University of Toronto unveiled a new AI algorithm taught by humans that learned beyond its training—they report that the system outperformed conventional systems by 160 percent. And a team at the University of Illinois described how they tweaked photosynthesis to boost crop yield—by boosting levels of three important proteins. A team at the University of Leeds reported on how they discovered a common cough virus that kills liver cancer cells and the hepatitis virus—reovirus, they found, stimulates the immune system, providing help in fighting both ailments. And there was more news about how Google and Facebook are taking aim at ‘fake’ news—which some have said may have actually influenced the outcome of the recent U.S. presidential election.And finally, a type of face that men recognize better than women—a pair of researchers at Vanderbilt University found that men are better at recognizing the faces on Transformer toys. This, the researchers claim, suggests that facial recognition may be more experience-based than thought. Explore further Distant star is roundest object ever observed in naturecenter_img The star Kepler 11145123 is the roundest natural object ever measured in the universe. Stellar oscillations imply a difference in radius between the equator and the poles of only 3 km. This star is significantly more round than the sun. Credit: Mark A. Garlick Citation: Best of Last Week—Roundest object ever found, taking aim at ‘fake’ news and one face men recognize better than women (2016, November 21) retrieved 18 August 2019 from https://phys.org/news/2016-11-weekroundest-aim-fake-news-men.html © 2016 Science Xlast_img read more